The accurate measurements of full-field surface shape, displacements and strains for objects that are immersed in a media that is different from where the optical measurement system is provided, is of great interest in a variety of applications. For example, measuring deformation of biological materials over an extended period of time, such as vascular arteries, usually requires that the material be fully submerged in an adventitial bathing media with controlled temperature and pH. According to Snell's law, when light travels through different media, it refracts at the interface. Sutton et al. (Development of a Methodology for Non-Contacting Strain Measurements in Fluid Environments Using Computer Vision, Optics and Lasers in Engineering. (32) 2000; 367-377) calculated and measured the strain errors introduced by refraction when a camera in air measures a planar specimen submerged underwater. This work has clearly shown that strain errors increase rapidly as the angle between the optical axis and the interface changes. When the angle is 12°, the strain is as high as 1%.
Thus, there remains a need for an accurate and effective way to correct distortion induced by refraction and to calibrate measurement systems for multimedia applications.